Strecks Java 5 Extensions

Transcription

1 Strecks Java 5 Extensions Presented by Phil Zoio, Realsolve Solutions March 17, 2006 (1)

2 Agenda Background and introduction The Details Form validation Data binding and conversion Actions Interceptors Navigation Concluding comments (2)

3 About Struts Most successful Java web framework First widely adopted MVC Model 2 framework Proven on thousands of projects Ground-breaking in its time but these days: Not universally popular Overtaken by other frameworks Various Struts initiatives Shale Struts Action 2 (WebWork integration) (3)

4 Some Background In-depth experience last year with Component-based frameworks (Tapestry/JSF) Dependency injection (Spring) Java 5 Requirement to build new web application in Struts Initially reluctant didn't want to forgo advanced features Decided to add features to existing Struts After completion of project Internal refactoring Additional features added To be open sourced Provisional name Strecks (4)

5 About Strecks Java 5 Extensions Built on existing Struts 1.2.x code base Main features include Pure POJO action beans Action dependency injection Action controllers Interceptors Form validation using annotations Data conversion and binding using annotations Pluggable navigation (5)

6 Strecks design goals offer or even improve on features offered by competitive frameworks simplify, not replace, existing Struts programming model no major high level architectural changes actions, action forms, etc. still present, but enhanced UI and configuration unchanged don't air your dirty linen in public users don't want to see framework internals introduce no compatibility issues apart from Java 5 keep easy to learn for existing Struts users (6)

7 (7) Strecks - The Details

8 (8) Form Validation

9 Form Validation in Struts 1.2 Manual validation code verbose and tedious XML-based validations using Validator framework not ideal: Large validation file Verbose format XML Hell (9)

10 Form Validation Struts 1.2 Example (10) if (days == null) { ActionMessage error = new ActionMessage("holidaybookingform.days.null"); errors.add("days", error); haserror = true; else { if (!GenericValidator.isInt(days)) { ActionMessage error = new ActionMessage("holidaybookingform.days.number ); errors.add("days", error); haserror = true;

11 Form Validation in Strecks Still uses ActionForm Interface between view layer and action forms unchanged Validation (and binding) layer within ActionForm Implement marker interface AnnotatedForm annotations to setters validate() method will still be called for additional (manual validation) Application not exposed to framework internals (11)

12 Form Validation Strecks = = "holidaybookingform.days.number") public void setdays(string days) { this.days = days; (12)

13 Adding Form Validators Easy to add validators Validator implements Validator interface public boolean validate(t value); Validator instance created by ValidatorFactory ValidatorFactory class identified by annotation Validation parameters passed in via annotation Called the Annotation Factory pattern Consequence: full extensibility with No XML No existing file changes (13)

14 (14) Data Binding And Conversion

15 Binding and Conversion in Struts 1.2 Use of richly typed ActionForms tricky No per-field control of type conversion Manual data binding code verbose and tedious (15)

16 Bind and Conversion Struts 1.2 Example public void readfrom(holidaybooking booking) { if (booking!= null) { if (booking.getstartdate()!= null){ this.startdate = new java.sql.date(booking.getstartdate().gettime()).tostring(); public void writeto(holidaybooking booking) { if (this.startdate!= null && this.startdate.trim().length() > 0) booking.setstartdate(java.sql.date.valueof(startdate)); (16)

17 Binding and Conversion in Strecks As with validation Binding and conversion layer within ActionForm Implement marker interface AnnotatedForm to annotations getters Add getters and setters for domain model objects Controller will call bind handlers Application not exposed to framework internals (17)

18 Bind and Conversion Strecks Example private HolidayBooking = = "yyyy-mm-dd") public String getstartdate() { return startdate; (18)

19 Adding Bind Handlers Bind handler implements BindHandler interface BindHandler instance created by BindHandlerFactory public void bindinwards(object src, String property); public void bindoutwards(object src, String property); BindHandlerFactory class identified by annotation Binding parameters passed in via annotation Converter class can be specified in annotation (19)

20 Adding Stand-alone Type Converters Converter can also be specified in own annotation Converter annotation in same method as bind annotation Converter implements Converter interface public T totargettype(s toconvert); public S tosourcetype(t toconvert); Converter instance created by Converteractory ConverterFactory class identified by annotation Converter parameters passed in via annotation Decouples bind handler and converter definition Used when converter must be parameterized (20)

21 (21) Dependency Injection

22 Dependency Resolution in Struts 1.2 State held in request, session and context attributes Verbose API Type casting necessary Not very object oriented Manual conversion of request parameters Service layer references obtained via programmatic hooks (22)

23 Dependency Resolution Struts 1.2 Example public ActionForward execute(actionmapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception { //use Spring ActionSupport superclass to get context HolidayBookingService service = (HolidayBookingService) getwebapplicationcontext().getbean( "holidaybookingservice"); long id = Long.parseLong(request.getParameter("holidayBookingId")); HolidayBooking holidaybookings = service.getholidaybooking(id); request.setattribute("holidaybooking", holidaybookings); return mapping.findforward("success"); (23)

24 Strecks Dependency Injection Actions instantiated on per-request basis Dependencies resolved declaratively via annotations Support for: Typed request parameters (using Converter) Request, session, application context attributes Spring beans, message resources, locale, ActionForm etc... (24)

25 Dependency Injection Strecks Example public String execute() { HolidayBooking holidaybookings = service.getholidaybooking(holidaybookingid); webhelper.setrequestattribute("holidaybooking", holidaybookings); return = "holidaybookingservice") public void setservice(holidaybookingservice service) { this.service = service; = true) public void setholidaybookingid(long holidaybookingid){ this.holidaybookingid = holidaybookingid;

26 Adding Dependency Injection Mechanisms Injection handler implements InjectionHandler interface public Object getvalue(actioncontext context); InjectionHandler instance created by InjectionHandlerFactory InjectionHandlerFactory class identified by annotation Injection parameters passed in via annotation Injection possible for any data obtained via request, response, application context, action mapping, action form (26)

27 (27) Actions and Controllers

28 Actions in Struts 1.2 Actions must be thread-safe No request-specific instance fields Request dependency injection impossible Single inheritance hierarchy Difficult to reuse request processing logic (28)

29 Actions in Strecks Implemented by combination of action controller and action bean Controller implements common request workflow Action bean handles domain-specific processing tasks (29)

30 Action Beans Pure POJOs Registered in struts-config.xml Identify controller using annotation Implement controller-defined interface Dependencies resolved via dependency injection Any request processing pattern can be abstracted into a controller. Action beans handle the fine grained domain specific action interactions (30)

31 Action Bean Example = BasicSubmitController.class) public class SubmitEditBookingAction implements BasicSubmitAction { public String cancel() { //implementation ommitted; public String execute() { //implementation omitted //injected properties (31)

32 Action Beans Example Implementation public String cancel() { webhelper.setrequestattribute("displaymessage", "Cancelled operation"); webhelper.removesessionattribute("holidaybookingform"); return "success"; public String execute(){ HolidayBooking holidaybooking = form.getbooking(); holidaybookingservice.updateholidaybooking(holidaybooking); webhelper.setrequestattribute("displaymessage", "Successfully updated entry: " + holidaybooking.gettitle()); webhelper.removesessionattribute("holidaybookingform"); return "success"; (32)

33 Action Controllers Defines action bean's interface Implement request processing workflow Instantiates action bean per request Interacts with action bean through interface Single instance, holds no request state Various out the box implementations, including form handling controllers dispatch controllers Single controllers reusable across many actions (33)

34 Controller Implementation = BasicSubmitAction.class) public class BasicSubmitController extends BaseBasicController protected ViewAdapter executeaction(object actionbean, ActionContext context) { BasicSubmitAction action = (BasicSubmitAction) actionbean; //omitted... figure out whether form is cancelled if (form instanceof BindingForm &&!cancelled) { //omitted... do binding and call prebind(); (34) String result = cancelled? action.cancel() : action.execute(); return getactionforward(context, result);

35 Action Bean Annotations Framework for adding behaviour through annotations ActionBeanAnnotationReader interface Extends contract between controller and action bean Fully extensible: no XML or source file changes Uses: Reading dependency injections Pluggable navigation Action bean source Singleton action beans (planned) Dispatch method lookup (35) Action-specific interceptors (planned)

36 (36) Interceptors

37 About Interceptors Most web applications have common operations: Logging Authentication Custom state management etc. In Struts 1.2, implemented either via: RequestProcessor subclasses Common Action base classes Interference with inheritance hierarchy (37)

38 Interceptors in Strecks Interceptor interfaces BeforeInterceptor AfterInterceptor Interceptors registered via configuration BeforeInterceptor Called after dependency injection Interrupt execution by throwing exception AfterInterceptor called before view handling Exceptions simply logged Neither can return navigation result (38)

39 Interceptor Example - Strecks public class ActionLoggingInterceptor implements BeforeInterceptor, AfterInterceptor { public void beforeexecute(object actionbean, ActionContext context) { HttpServletRequest request = context.getrequest(); log.info("starting action for " + request.getrequesturi()); log.info("using " + actionbean.getclass().getname()); public void afterexecute(object actionbean, ActionContext context) { HttpServletRequest request = context.getrequest(); log.info("ended action for " + request.getrequesturi()); (39)

40 Struts Extensions Action Invocation Controller Request Processor Controller Delegate Controller Action POJO Action Bean Interceptors extends RequestProcessor minimal implementation Implements extended behaviour Extends Action Implements request workflow POJO with DI Named in struts-config.xml IDs controller using annotations Either pre- or post Module-specific zero or more delegates to instantiates, injects dependencies beforeexecute() execute() Action Forward calls methods, executes workflow afterexecute() (40)

41 (41) Navigation

42 Navigation in Struts 1.2 Navigation via returning ActionForward Can be created manually or via actionmapping.findforward() But limited support for alternative view rendering Typically implemented: Within action, with null ActionForward returned Forwarding to external servlet (e.g VelocityStruts) (42)

43 Navigation in Strecks Two sets of controller implementations public String method() result gets ActionForward (outcome-based navigation) other uses pluggable navigation annotation Convenient solution vs flexible solution (43)

44 Basic Controller = BasicController.class) public class ExampleBasicAction implements BasicAction { private String message; public String execute() { message = "Executed " + ExampleBasicAction.class.getName(); return "success"; // public String getmessage() { return message; (44)

45 Navigable Controller = NavigableController.class) public class ExampleNavigableAction implements NavigableAction { private String message; public void execute() { message = "Successfully public String getresult() { return "success"; (45) public String getmessage(){ return message;

46 More on Navigation Controllers return ViewAdapter (not ActionForward) ActionForwardViewAdapter class RenderingViewAdapter interface ViewAdapter allows support for alternative view rendering mechanisms Allows, for example, rendering via Spring views AJAX, Remoting, XSLT, etc. easily supported Support for page classes for supporting formatting logic Support for redirect after post (46)

47 (47) Summary

48 Conclusion Strecks's aim has been to: Match the simplicity of Struts Match the validation and type conversion power of JSF/Tapestry Match the flexibility of Spring MVC and WebWork (48)

49 Who Should Use Strecks? Good solution for enterprises which: Have invested in Struts Developer knowledge Existing applications Want to take advantage of powerful Java 5 features Want a framework supporting modern best practices Ease of testability Use of interfaces, design patterns & good OOP dependency injection Want these features now BUT Don't want the pain of a bigger migration (49)

50 Current Status Ready for open source release Nearly version 1.0 ready Should be announcement very shortly Any help would be appreciated... (50)